This invention relates to an optical scanning type system for sequentially introducing a light beam into a plurality of optical wave guides, and in particular to an optical scanning type system for directing a laser beam of uniform intensity distribution onto a region of interest of a human subject.
As a light beam type apparatus, use may be made of a laser beam type medical treating device. It has proven effective to direct a ruby laser or argon laser onto a region of interest of a human subject, such as superficial pigmentation.
The energy distribution of a laser beam is, in general, the Gaussian distribution. In this connection it has been found that the mere irradiation of the surface of a living body with a laser beam causes burn spots, an undesirable side effect of medical treatment.
Japanese Patent Application No. 56-27816 discloses the technique of obtaining a laser beam of uniform energy distribution. In this technique, a laser beam is led into a plurality of, for example, glass prisms, where it is totally internally reflected, with the result that the resultant light beam of Gaussian energy distribution emerging from the prism is converted to a light beam of uniform distribution.
However, in this technique a laser beam of high momentary output, such as a pulsed laser beam, can be output from the prism as a laser beam of greater output density, while a laser beam of continuous output, such as an argon laser beam, emerges from the prism as a light beam of smaller output density, so that it takes a longer time to apply a laser beam of the desired energy level to the region of interest of a human subject, such as a superficial pigmentation, in which case sound or healthy living tissue around the pigmentation region will be destroyed due to the heat of the laser beam, thereby causing an undesirable treatment-related problem.
One solution to this problem has been proposed in U.S. Pat. No. 4,534,615, one of whose inventors is Kenji Iwasaki, one of inventors of this application. In this apparatus, a laser beam which is generated from a laser beam generator sequentially enters a plurality of optical fibers having a predetermined array of end faces, then sequentially enters Kaleidoscopes (trade name) bundled in a prismatic array which are coupled to the corresponding optical fibers, and leaves the kaleidoscope bundle. In this case, the laser beam is converted from a light beam of Gaussian energy distribution to a light beam of spatially uniform energy distribution. The laser beam leaving each kaleidoscope has an output density L as given below: EQU L =4W/S
where
W =the output level of the laser beam generated from the laser beam generator. PA1 S =the area of the exit end of the respective kaleidoscope. PA1 means for generating a laser beam; PA1 first reflection means for reflecting the generated laser beam; PA1 optical means arranged at a predetermined pitch and having a number of light-receiving sections into which the reflected laser beam is introduced; and PA1 a moving mechanism for moving either one of the first reflection means and optical means stepwise in a specified direction, to allow the reflected laser beam to sequentially enter the respective light-receiving sections of the optical means, PA1 in which the moving mechanism comprises means for generating a drive force, a cam body having a cam surface defining a number of steps having a varying height, the steps being so formed as to have a pitch corresponding to the pitch of the respective light-receiving section, and a cam follower mechanically coupled to either one of said first reflection means and optical means to allow the cam follower to follow the surface of the cam body.
As will be understood from this equation, if the area of the exit end face of the respective kaleidoscope is constant, then a laser beam of adequate and uniform intensity can be directed to a whole region of the aforementioned kaleidoscope bundle. The laser beam (argon laser beam) generator, taken in combination with the aforementioned apparatus, permits an argon laser to be directed to the region of interest at predetermined density over a broader exposure range.
In order to sequentially introduce a focused laser beam into individual optical fibers in a bundle, a tilting mirror is tilted stepwise by means of a step motor, to cause the laser beam reflected on the tilting mirror to be directed in a fan-shape to permit it to be launched into optical fibers bundled in a linear array. Therefore, there is a risk that a laser beam will not be uniformly introduced into the individual optical fibers due to a variation in the angle of incidence of the laser beam going into the end faces of the individual optical fibers. Since, moreover, the amount of laser beam to be introduced into the respective optical fibers depends upon the uniform rotation of the step motor as well as the tilt angle of the tilting mirror, there is also a risk that a constant amount of laser light will not invariably be introduced into the individual optical fibers.
A solution to this problem is also proposed in the aforementioned U.S. Patent in which, in place of the combination of the tilting mirror and step motor, use is made of a gear mechanism whereby a laser beam focused by a convergent lens after it has been generated from a laser beam generator is linearly moved along a linear array of end faces of bundled optical fibers, to allow it to enter the individual optical fibers. However, there is a possibility that a constant amount of laser light will not invariably be launched into individual optical fibers due to a variation in the pitch of the gear.
The aforementioned U.S. Patent further discloses a system in which the light exit end of the optical fiber, onto which a laser beam is focused by a convergent lens after it has been generated from a laser generator, is moved by a step motor along a rotation locus so that optical fibers arranged along said rotation locus can receive said laser beam in a sequential fashion. However, this method has a drawback, in that a constant amount of laser beam cannot invariably be launched into the individual optical fiber due to the use of the step motor.